LinuxQuestions.org - [SOLVED] disappearing partition trick, formatting micro sd, and random space consumed

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disappearing partition trick, formatting micro sd, and random space consumed

First off I'd like to say sorry for starting a thread in General. I was thinking about starting it under hardware since its related to an SD card, then I was thinking I should put it under software since its related to mkfs. I was also thinking about going under the slackware area because I'm slacking. But hey....general seemed good.

Maybe someone can help me understand what I'm doing wrong, or at least sympathize and confirm the problem is real and not just in my head.

So I fdisk a new partition and it shows up. Then I mkfs.vfat mmcblk0p1 and it vanishes.

Code:

cg132@laptop:~$ sudo dd if=/dev/zero of=/dev/mmcblk0 bs=1M count=1

1+0 records in

1+0 records out

1048576 bytes (1.0 MB) copied, 0.0925948 s, 11.3 MB/s

cg132@laptop:~$ sudo /sbin/fdisk -l /dev/mmcblk0



Disk /dev/mmcblk0: 67.1 GB, 67108864000 bytes

4 heads, 16 sectors/track, 2048000 cylinders, total 131072000 sectors

Units = sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes



cg132@laptop:~$ sudo /sbin/fdisk /dev/mmcblk0 

Welcome to fdisk (util-linux 2.21.2).



Changes will remain in memory only, until you decide to write them.

Be careful before using the write command.



Device does not contain a recognized partition table

Building a new DOS disklabel with disk identifier 0xd48f9117.



Command (m for help): n

Partition type:

  p  primary (0 primary, 0 extended, 4 free)

  e  extended

Select (default p): p

Partition number (1-4, default 1): 

Using default value 1

First sector (2048-131071999, default 2048): 

Using default value 2048

Last sector, +sectors or +size{K,M,G} (2048-131071999, default 131071999): 

Using default value 131071999

Partition 1 of type Linux and of size 62.5 GiB is set



Command (m for help): w

The partition table has been altered!



Calling ioctl() to re-read partition table.

Syncing disks.

cg132@laptop:~$ sudo /sbin/fdisk -l /dev/mmcblk0



Disk /dev/mmcblk0: 67.1 GB, 67108864000 bytes

4 heads, 16 sectors/track, 2048000 cylinders, total 131072000 sectors

Units = sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0xd48f9117



        Device Boot      Start        End      Blocks  Id  System

/dev/mmcblk0p1            2048  131071999    65534976  83  Linux

cg132@laptop:~$ sudo /sbin/mkfs.vfat /dev/mmcblk0p1 

mkfs.fat 3.0.22 (2013-07-19)

cg132@laptop:~$ sudo /sbin/fdisk -l /dev/mmcblk0



Disk /dev/mmcblk0: 67.1 GB, 67108864000 bytes

4 heads, 16 sectors/track, 2048000 cylinders, total 131072000 sectors

Units = sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes



cg132@laptop:~$ ?

What the heck? So I tried again with 10M block size

Code:

cg132@laptop:~$ sudo dd if=/dev/zero of=/dev/mmcblk0 bs=10M count=1

1+0 records in

1+0 records out

10485760 bytes (10 MB) copied, 2.53113 s, 4.1 MB/s

cg132@laptop:~$ sudo /sbin/fdisk /dev/mmcblk0 

Welcome to fdisk (util-linux 2.21.2).



Changes will remain in memory only, until you decide to write them.

Be careful before using the write command.



Device does not contain a recognized partition table

Building a new DOS disklabel with disk identifier 0x48d894ce.



Command (m for help): n

Partition type:

  p  primary (0 primary, 0 extended, 4 free)

  e  extended

Select (default p): p

Partition number (1-4, default 1): 1

First sector (2048-131071999, default 2048): 

Using default value 2048

Last sector, +sectors or +size{K,M,G} (2048-131071999, default 131071999): 

Using default value 131071999

Partition 1 of type Linux and of size 62.5 GiB is set



Command (m for help): w

The partition table has been altered!



Calling ioctl() to re-read partition table.

Syncing disks.

cg132@laptop:~$ sudo /sbin/fdisk -l /dev/mmcblk0



Disk /dev/mmcblk0: 67.1 GB, 67108864000 bytes

4 heads, 16 sectors/track, 2048000 cylinders, total 131072000 sectors

Units = sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x48d894ce



        Device Boot      Start        End      Blocks  Id  System

/dev/mmcblk0p1            2048  131071999    65534976  83  Linux

cg132@laptop:~$ sudo /sbin/mkfs.vfat /dev/mmcblk0p1 

mkfs.fat 3.0.22 (2013-07-19)

cg132@laptop:~$ sudo /sbin/fdisk -l /dev/mmcblk0



Disk /dev/mmcblk0: 67.1 GB, 67108864000 bytes

4 heads, 16 sectors/track, 2048000 cylinders, total 131072000 sectors

Units = sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x48d894ce



        Device Boot      Start        End      Blocks  Id  System

/dev/mmcblk0p1            2048  131071999    65534976  83  Linux

cg132@laptop:~$ sudo mount /dev/mmcblk0p1 /mnt/floppy/

cg132@laptop:~$ df -h

Filesystem      Size  Used Avail Use Mounted on

/dev/sda3        22G  18G  2.9G  86% /

/dev/sda1      976M  17M  892M  2% /boot

tmpfs          3.8G    0  3.8G  0% /dev/shm

/dev/mmcblk0p1  63G  20G  44G  31% /mnt/floppy

cg132@laptop:~$ D-:

Wow! Now my partition is there after mkfs but 20gb has been eaten by gremlins. Now what? Should I skeet shoot this card and be done with it? I used it to store a video game install. The card was always readable and reinstalled the game without a problem so I don't think the card is bad.

How do I get my 20gb back? The card is blank as far as I can tell. Any suggestions?

Cheers
132

I don't see you doing anything wrong. Perhaps the card is broken: http://forums.anandtech.com/showthread.php?t=2335234 (and many more links when you google for "check sd card").

The card is not bad. I've been using it to store a very large video game install, about 30gb, and the data always came back clean. Just to be sure I formatted the card in windows without issue. Trying not to advocate windows here but it seems to handle the card just fine. I flip over to *nix and the card acts normal now that windows molested it. I use SD cards frequently, and I've thrown out quite a few over the years, but I've never seen this before. Well I've seen all kinds of hocus pocus including the disappearing partition table, file system corruption, and dead cards that take data and comes back with gibberish. However I've never seen 20gb of gremlins consuming the card without any files being present. Thought I'd bring it up here to see if there was a solution. Figured there must be a better way to do things. I must admit this is the only SDXC(64gb) card I have. I haven't seen this problem on any SDHC(32gb) cards. I was saying I should skeet shoot it just to prevent the gremlins from spreading across my network, the internet, and possibly take over the world! :-P

Found my problem. EXFat. You can slap me with a rotten fish now. Guess SDXC requires exfat. vfat, ext2, ext3, ext4, reiserfs, jfs....none of them work. But exfat does. <sigh>

Thanks for the postback. That is seriously twisted.

Another thing I noticed is that in fdisk, you are not changing the partition type label to FAT. You're leaving it on "Linux". It really should be on one of the FAT options instead. That can be done with a "t" command in fdisk.

Checked....didn't help.

Code:

cg132@laptop:~$ sudo /sbin/fdisk -l /dev/mmcblk0



Disk /dev/mmcblk0: 67.1 GB, 67108864000 bytes

252 heads, 59 sectors/track, 8815 cylinders, total 131072000 sectors

Units = sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x00000000



        Device Boot      Start        End      Blocks  Id  System

/dev/mmcblk0p1            2048  131071999    65534976    b  W95 FAT32

cg132@laptop:~$ sudo /sbin/mount /dev/mmcblk0p1 /mnt/floppy/

cg132@laptop:~$ df -h

Filesystem      Size  Used Avail Use% Mounted on

/dev/sda3        22G  19G  2.4G  89% /

/dev/sda1      976M  17M  892M  2% /boot

tmpfs          3.8G    0  3.8G  0% /dev/shm

/dev/sda2      137G  125G  12G  92% /windows

/dev/mmcblk0p1  63G  20G  44G  31% /mnt/floppy

Just to be extra sure. I created a linux type partition table and formatted it with exfat. Looks better than the mess windows made of the partition table.

Code:

cg132@laptop:~$ sudo /sbin/fdisk -l /dev/mmcblk0 



Disk /dev/mmcblk0: 67.1 GB, 67108864000 bytes

4 heads, 16 sectors/track, 2048000 cylinders, total 131072000 sectors

Units = sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes



cg132@laptop:~$ sudo /sbin/fdisk /dev/mmcblk0 

Welcome to fdisk (util-linux 2.21.2).



Changes will remain in memory only, until you decide to write them.

Be careful before using the write command.



Device does not contain a recognized partition table

Building a new DOS disklabel with disk identifier 0xf6d89914.



Command (m for help): p



Disk /dev/mmcblk0: 67.1 GB, 67108864000 bytes

4 heads, 16 sectors/track, 2048000 cylinders, total 131072000 sectors

Units = sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0xf6d89914



        Device Boot      Start        End      Blocks  Id  System



Command (m for help): n

Partition type:

  p  primary (0 primary, 0 extended, 4 free)

  e  extended

Select (default p): p

Partition number (1-4, default 1): 

Using default value 1

First sector (2048-131071999, default 2048): 

Using default value 2048

Last sector, +sectors or +size{K,M,G} (2048-131071999, default 131071999): 

Using default value 131071999

Partition 1 of type Linux and of size 62.5 GiB is set



Command (m for help): w

The partition table has been altered!



Calling ioctl() to re-read partition table.

Syncing disks.

cg132@laptop:~$ sudo /usr/sbin/mkfs.exfat /dev/mmcblk0p1 

mkexfatfs 1.2.1

Creating... done.

Flushing... done.

File system created successfully.

cg132@laptop:~$ sudo /sbin/fdisk -l /dev/mmcblk0 



Disk /dev/mmcblk0: 67.1 GB, 67108864000 bytes

4 heads, 16 sectors/track, 2048000 cylinders, total 131072000 sectors

Units = sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0xf6d89914



        Device Boot      Start        End      Blocks  Id  System

/dev/mmcblk0p1            2048  131071999    65534976  83  Linux

cg132@laptop:~$ sudo mount /dev/mmcblk0p1 /mnt/floppy/

FUSE exfat 1.2.1

cg132@laptop:~$ df -h      

Filesystem      Size  Used Avail Use% Mounted on

/dev/sda3        22G  19G  2.4G  89% /

/dev/sda1      976M  17M  892M  2% /boot

tmpfs          3.8G    0  3.8G  0% /dev/shm

/dev/sda2      137G  125G  12G  92% /windows

/dev/mmcblk0p1  63G  2.8M  63G  1% /mnt/floppy

cg132@laptop:~$